Since the day their mother Aline remarried, Patrice and Eric, a joyful pair of twins, have been very happy. Indeed, François Chantour, their stepfather, is very kind and behaves like a big brother to them. Even if they are not very rich, the four of them live a cheerful life in their charming house. The trouble is that, in Lyon, the family on the boys'father's side are worried, especially the twins' grandmother, who fears Patrice and Eric are given a bad education. She therefore brings them to her big house in the hope of their improving their manners. A very unfortunate decision indeed...